1. Field of the Invention
This invention relates to a clutch device.
2. Description of the Related Art
A friction clutch using a friction plate has gained a wide application as a clutch device for interruptedly transmitting power generated by a driving source to a driven body. Examples of such a friction clutch includes a clutch to be combined with a manual transmission of a car, a so-called "lockup clutch" disposed inside a torque convertor of an automatic transmission, and so forth.
On the other hand, a variety of prime movers are used as the driving source, and most of the prime movers involve a torque change during one cycle of rotation.
In reciprocating-piston-type internal combustion engines that have been most widely employed for cars, for example, the torque change occurs due to reciprocation of the pistons and due to the pressure change inside a combustion chamber, and an axle rotates with a torque change and with a rotation change.
If this change is transmitted to the driven body, the driven body vibrates and in the case of the car described above, for example, this vibration is transmitted to the car body, so that a driver feels uncomfortable and the commercial value of the car is lowered.
Therefore, a power transmission apparatus which reduces the frictional engagement force of a friction clutch to prevent transmission of the torque change of the engine to the car body and transmits power while slipping the friction clutch is known (Japanese Unexamined Patent Publication (Kokai) No. 57-33253).
Nonetheless, slip of the friction clutch means conversion of a part of power inputted from the prime mover to heat energy and to discard it, and results in a great waste of energy.